This invention relates to an apparatus for automatic bundling of sheet material.
U.S. Pat. No. 3,996,728 describes such an apparatus for paper sheets wherein paper sheets are transported between two conveyer belts driven in synchronism to two plates disposed parallel at the same distance as the conveyer belts. The distance between the conveyer belts corresponds to the stack height. Since the upper plate is vertically adjustable, the distance between the plates can be adjusted in accordance with the height of the supplied stack. Before the paper sheets reach the plate plane, the plates move in the direction of a foil extending perpendicular to the plate plane. The stack of sheets guided between the plates by the conveyer belts thereby hits the foil so that the foil is carried with the stack. The stack of sheets is then conveyed out of the plate plane whereby the foil is cut to the right stack format. The stack of sheets is then supplied via a separate transport path to an apparatus which brings together and interconnects the two foil ends. The known packing apparatus therefore has relatively great dimensions. Further, the known packing apparatus offers insufficient flexibility in processing stacks of sheets having different heights since the distance between the conveyer belts and thus the maximum stack height between the conveyer belts is firmly preset.
The invention is thus based on the problem of proposing an apparatus of the abovementioned kind which has a space-saving design and offers high flexibility in bundling different stack formats.
Sheet material to be bundled is preferably clamped as a stack between two parallel conveyer belts, the distance between the conveyer belts being adaptable to the particular stack format by automatic vertical adjustment of the conveyer belts. This permits compensation of differences in stack height which are due for example to quality differences of the sheet material. For example, the stark height of bank notes can vary greatly despite the same number of bank notes to be bundled by reason of their different states (greatly soiled or little soiled). Further, clamping the stack of sheets between the conveyer belts permits exact positioning of sheet material while it is being banded. Since the conveyer belts are used for fixing the sheet material to be bundled, on the one hand, and for transporting the bundled sheet material for the purpose of further processing, on the other hand, one can achieve a compact structure of the bundling apparatus whereby the bander, which guides the foil around the stack of sheets positioned between the conveyer belts and connects it into a band, can be disposed between the supplied foil and the conveyer belts in space-saving fashion.
According to a development, sheet material to be bundled is deposited in a precisely fitting stack on a vertically adjustable lifting table and urged against an opposite plate until a defined pressing force is reached. Alternatively the sheet material can be deposited on the lifting table as a stack with a certain desired height without the sheet material being compressed with a predefined pressing force. The stack of sheets is then drawn in by the conveyer belts, the vertical adjustment readjusting the distance between the conveyer belts with the aid of a proximity switch so as to produce a continuous channel between the lifting table and a conveyer belt. Since vertical adjustment does not change the length of the toothed belt for driving the conveyer belts, it can be effected during operation of the conveyer belts without intervention by the operator. Vertical adjustment of the conveyer belts and also the lifting table thus permits processing of different sheet formats which vary in particular with respect to their stack height. One can also use different foil widths for bundling the sheet material, as well as adjust the foil position.
Further advantageous developments of the invention can be found in the description with reference to the figures, and the dependent claims.